cos(a-B/2)=-5/13,sin(a/2-B)=4/5,且0

sin(a-b)*cos a-cos(a-b)*sin a=1/5,则cos 2b的值是 Cos(a+b)*cos(a-b)=1/5 求cos ^2-sin^2 cos(a-b)=12/13,sin(a+b)=-3/5,求cos(pai/2-2a)如题～ sin(a+b)=4/5cos(a-b)=12/13求cos 2a=? sin(a+b)cosa-cos(a+b)sina=5/13 则sin（π-B)=? 证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2B=1 cos^2a-cos^2b=m,那么sin(a+b)sin(a-b)=? 证明sin(A+B)sin(A-B)=cos^2B-cos^2A cos(a+b)cos(a-b)+sin(a+b)sin(a-b)=-3/5,求sin(3π/2+2b) cos(a-B/2)=-5/13,sin(a/2-B)=4/5,且0 已知sin(a+b)=-3/5,cos(a-b)=12/13,且π/2 求证cos(a+b)cos(a－b)=cos^2b－sin^2a 求证cos(a+b)cos(a-b)=cos^2a-sin^2b 由cos(a+b)=cos a cos b-sin a sin b cos(a-b)=cos a cos b+sin a sin b解题设a为锐角,证：1、2分之根3乘cos a + 2分之1乘sin a=cos(6分之π-a)2、cos a-sin a=根号2cos(4分之π+a) 已知sin[a-b]cos a-cos[b-a]sin a=3/5,b是第三象限角,求sin[b+5π/4]的值第一题1/2cos x-√3/2sin x第二题√3sin x+cos x第三题√2[sin x-cos x]第四题√2cos x-√6sin x 已知向量a=(cosα,sinα),b=(sinβ,cosβ),β属于(0,π),tanβ/2=1/2,向量ab=5/13．求sinβ,cosβ,sinα求详解 cos(a+b)=-5/13 sinb=3/5,a,b为锐角求cos(a+2b)求sin a 已知cos(a+b)=-1/3,cos 2a=-5/13,a,b均为钝角,求sin(a-b)